Study And Comparison Of Chemical Thermodynamic And Kinetic Calculation Of Representative Trace Elements In Coal Combustion Process

The main way to utilize coal, which is a main kind of energy source in China, is burning. But coal combustion will bring great pollution to the environment and do harm to the health of human beings and life of wild plant and animals, and it will even affect the progress of sustainable economic development in China. Emission and control of trace element (TE) from coal combustion is now an emerging and frontier area and going to attract more attention in future. In this paper, the trace elements was comprehensively presented at first from seven aspects, such as definition, origination, harm, content in coal, kind, transform mechanisms and lately study progress. The thesis then introduced the method of chemical equilibrium analysis, and F*A*C*T, the software of chemical thermodynamics was used to predict the speciation of six kinds of trace elements, that is mercury, cadmium, arsenic, lead, chromium and nickel in flue gases during coal combustion. Especially, oxidant of sulfur and minerals of calcium and silicon were taken into account to include in the models of equilibrium. At the same time, the theory of chemical kinetics was also referred and the procedure CHEMKIN-III , just programmed according to the theory, was utilized to describe accurately reaction products and their concentrations-time correlation of mercury and chromium. Speciation of mercury and chromium in combustion-generated flue gases was modeled by detailed kinetic model. The results from the model kinetic calculation are in reasonable agreement with Mamani-Paco and Widmer's experimental data.Finally, the results of models of chemical thermodynamics and kinetics were combined and compared for the example of mercury and chromium. The thermodynamic calculation help to set up the kinetic models. The results of the two were similar and errors maybe were caused by: (1) the errors of the kinetic parameters in oxidation mechanism; (2) the errors of choice of reaction time in the thermodynamic analysis; (3) the errors of the equilibrium calculation.